This invention relates to surgical apparatus suitable for use during tibia/femur osteotomy for total knee replacement, or a proximal tibia osteotomy for corrective knee structuring. More specifically, the apparatus of this invention is universal in that means are provided for precisely maintaining a cutting plane, precisely determining the necessary amount of bone to be removed and for guiding osteotome blade for precisely removing such amount of bone.
Osteotomy is an operation upon bone which involves cutting the bone and sometimes removing or adding portions of the bone and also includes moving bone parts in space relative to one another. In a similar manner, prosthetic surgery often involves the excision and removal of deteriorated and diseased bone tissue in either the knee and hip joints and has now has become quite common. In many instances, artifical members of plastic and/or metal which is compatible with the body systems are substituted for the removed natural bone. Such artifical members or joints are available for both knee and hip bone structures.
In particular, the bearing surface of the knee joint is vulnerable to stress, arthritic and other disease induced deterioration. Prosthetic correction is indicated when the tissue becomes so damaged that other less drastic techniques have little or no prospect of success. Thus, there has been developed various surgical techniques ranging from corrective surgery all the way to total knee replacement. In particular, surgery which is somewhat less extensive than total knee replacement includes "high tibia osteotomy". High tibia osteotomy or proximal tibia osteotomy is particularly useful where a patient has a varus deformity of the knee. That is, one or both knees bow outward at an angle significantly greater than the desired valgus position of 5 to 8 degrees. A proximal tibia osteotomy may be specifically performed to change from a varus to a valgus position of 5 to 8 degrees and thereby shift the weight bearing load of the knee from the medial to the lateral compartment. This type of corrective surgery also achieves a smooth congrous osteotomy surface and avoids violation of the knee joint itself. In practice to date, there has been significant problems and factors which detrimentally affect the clinical judgement in the operating room such that very accurate proximal tibia osteotomys are difficult to obtain. For example, recent articles presented to the AAOS (American Association of Orthapedic Surgeons) indicate difficulties with osteotomy procedures because of factors which affect the clinical judgement of the surgeon in the operating room. In particular, an article entitled High Tibial Osteotomy Revisited written by Dr. James J. Elting, Dr. William R. Hopper, and Dr. Larene E. Lane, of the Aurelia Osburn Fox Memorial Hospital in Oneonta, N.Y. points out some of the difficulties with respect to the osteotomy procedure. For example, on page 1, the article states that "precise measurements of the femoral-tibial angle is impossible either roentgenograhically or clinically" and at page 2 that "precise measurement is impossible, by any means". Thus, it is seen that sucessful surgeons are willing to present medical papers to their peers admitting to the difficulty or the impossibility of obtaining precise measurements in proximal tibia osteotomy surgery. However, as will be discussed hereinafter, the present invention allows precise measurements rather than depending upon rules of thumb such as a one millimeter of bone wedge to be removed per degree of correction". Other factors affecting the clinical judgement include the thickness of the soft tissue and the magnification caused by x-ray etc. Thus, it will be appreciated that any kind of technique or apparatus which provides precise measurement to determine the wedge of bone to be removed during a proximal tibia corrective osteotomy would be a major advancement in such surgical techniques.
It would be of particular value if such an apparatus suitable for providing precise measurements for proximal tibia osteotomys could also be used as standard equipment for total knee replacement osteotomys. Thus, the surgeon would become more familiar with the equipment. Although an investigation of the available prior art failed to reveal any type of apparatus relevant to the present invention, several patents that were discovered are discussed hereinafter, and may be referred to for reference as typical types of apparatus. For example, U.S. Pat. No. 3,728,742 issued to Robert G. Averill et al. on Apr. 24, 1973 discloses a total knee or elbow prosthesis. According to this patent the complete knee or elbow joint may be replaced with metal or plastic type components if the original joint has been destroyed by arthritis or other disease or accident. Reference to this patent will reveal the type of surgical bone removal that must take place for such total knee replacement as is also discussed in the present invention.
In addition, measuring devices used to insert a pin in a hip bone is described in U.S. Pat. No. 4,037,592 issued to Richard F. Kronner on July 26, 1977. This device provides a tool and method such that surgeons may carefully insert a hip nail guide pin within the upper end of the femur. Earlier nail guides for the femur include one disclosed in the U.S. Pat. No. 2,200,120 issued to W. W. Nauth on May 7, 1940 and U.S. Pat. No. 2,737,724 issued to J. R. Herz on Mar. 13, 1956. Reference to these patents quickly indicates that in no way are they relative to osteotome blade guides useful in a proximal tibia osteotomy or a total knee replacement osteotomy. However, these patents do show that measuring devices are useful and accepted by surgeons when they can be directly used to take the guess work out of a surgery technique.
In addition to the above discussed patents, other references may be had to apparatuses available from the Zimmer Company of Warsaw, Ind. which provides surgical apparatus, or the Orthopedics Division of Howmedical, Inc. which also provides apparatus for total knee replacements and proximal tibia osteotomys. Reference to all of these materials clearly indicates that even with the use of presently available apparatus, a great deal of clinical judgement and guess work is required in the operating room during the osteotomy surgery.